Wave generator



4 1943 M. cAwElN WAVE GENERATOR Filed Jan. 11, 194s 2 Sheets- Sheet l muv' F:

A m F v mvENToR TIME ATTORY May 4, i948. vM. cAwElN WAvE GENERATOR Filed Jan. 1l, 1943 2 sheets-sheetv 2 ATToR Patented May 4, 1948 ese assignments, to Farnsworth cornemuse; c corporation. cf indiana Research Applicaticn January 11, 194s, .scrjialnd mimi.' Y

14 clams'. (cl. 250436) 1 This invention relates togencratorsof periodic `Waves of complex `forni and particularly .t gen'- erators of the oscillator type for Prolduc-h odio currents having a complexwave' forni.

According to conventional practice in .th.. 1 1`S e y of tubes ,employing beams f electrons, Asuch .as .81 dissector tube ll'Sedat the transmitter virl alzielv vision system, `or a cathode raytube .used at the receiver in such asystem, itis ustonary t deectthe electronbeam for sca ningfpj eS ynymeans ofeither anelcctrostaticio aelelctro.-

magnetic ucla. Tnesjcnelds are requirente have saw-toothed Wave forms. `Wl'eeit is desiredto produce an electromagnetic .eld Oifl sawtooth wave form it is necessary to supply,` tothefdeyfleeting coils of the tube, periodic current of such wave form that. the fieleA .win have' thedesgirecl saw; to othed.w ave form Numerous. currentfg'enerators of the oscillator type thave been prop, 'Seli forsuch a purpose. flxpica1.cf 'uch oscil1atn rs is that disclosed in united. .States Patent '.No.

2,059,683. granted to-Prina Farnsworth on No;

vcmber 3, 1936. limitation cgftnis type ofrenerator is that, for certain uses, i t is incapable 0f Supplying currents cf Asuiicient,:nac.rllitudeg- An object .of the presentinvention .there orge,

-is to' provide an improved oscillator forgenerating periodic current waves of comnlex.iorm. suoh as, for example', waves of saw-tooth unrelated efficiencythan heretofore obtainable.

Alstillffurther objectofl-theinvention iste-pro"- vide-a-saw-tooth oscillator having sufficient Ycircuit nexibiiity to be adaptable,bysimpieswitchF ing. means, vfor operationat Widely diierentrreiquencies.

Another object/of the -inventionis to providea novel electronic means -for Acoritrollinig theirates of increase-and ydecrease ...of current .in -a-icireuit which includes inductance and-resistance.,

In an effort to .modityan oscillator of ,the vtype disclosed in the Farnsworthgpatent vreferrel to for .the production `of larger deflectioncurrents ofzbetter waveforms. a beam .power .typetnbeyvgas substituted for the tetrpde usedlliyr'ajrnsworth- The other circuit coxnloonfre'ntsy were retained withoutfsubstantial valteration except-inthe constants thereof. However, the substitution of the beam power tube forthe tetrodev produced results-which were-considerably beyond-'the scope o-f-11easonable 2, expectancynnd constituted material improvements over .the results ,obtnnnblewich the Earns; oscillator. The .generated Current WnS found'tohave a' smaller semiexponential corn- POneni than heretofore therein ,constituting en inaproreniennin tnewave form 'There was also found to be a substantial vincrease in the magnitude'cf the generated current. -Incidental to, or pernapsinsrrnrnennl the production of there 'imnrove resultan.Was-discovered thni'ine .Controlof the frequency and amplitude characteristics of the generateQLWaVeWa/s efetedin a manner differingiromythe control of the corresponding nnrnoft'erstirisin the Farnsworth oscillator. Thus, cut-oi is relatively, absolute andresults in a relatively 4steeper wavefront than in other existingV circuits.

in accordance with the present invention there iswprovided any oscillator for generating large ,periodic currents ,Qfgnomrlen were `linnn, which power tube; adaptedyto xform a concentrated electron beam. There is connected in the anode or output circuit o f the tube anjinductance. An- `other i.nductance closely coupled tothe anode rinductanc'e is connected in the control lgrid or inputV circuit of vthe tube, A'Ifhe Yinductances are poled so that an increasein anode current will apply a positivepotential of such magnitude to jthe grid'that `the impedance ofthe tube is reduced -to a.Y relatively'low value. A positive potential of predetermined magnitude is connected to the screen ,grid'o'f the' tube throughan impedance. The (periodiccurrent Wave offcomplex form is derived from the'inductancecpnnectedto the con- -trol grid ofthe tube. If desired, high Voltage pctentials may Abe derived from the anode `in- ;ductance Whichniaybe rectified to produce ahgh -coltage 4direct current.

There are Valso provided :facilities -for changing the frequency of the "generated currentwave without effecting any aplnrecialole` change in the amplitude -Vthereof.- Additional faclities'arevproe vided for making refinements in the Waveform vofthevgenerated Waveto-render it more suitable for use deecting coils Afor the production -ef 'an-electreiagneticfield ior'scanning purposes.

For a Ybet-terf-understajnding of the invention, together iwith other and furthervobjects thereof, vr'e'vfeinr'ice jshad'to-theefollowing description taken in connection -wi-th Fthe accompanying drawings and itssccpefwilibepcintcd out-inthe appended claims.'

Vlijst-he accompanyingdrawings: VFigi; 11 `is --afcircuit `diagram Vof an oscillator for generating" periodic current Wavesof a complex A:forni Vembodying the present invention;

Vvflig: 2il1u'strates-avseries ofcurves characteristi-c of-voltages appearing in some of the `circuits indcis Figs. 3 and 4 show modied circuit connections between the output terminals of the oscillator and the deiiecting coils of a tube of the cathode ray type;

Fig. 6 is a further modification of theioscillator of Fig. 1 which incorporates'facilities for producing periodic waves of improved wave form.

Referring now more particularly to Fig. 1 of, the drawings, the oscillator embodying the pres-v ent invention includes a beam power tube I0, having va cathode II, a control grid I2, a screen grid I3, beam-forming elementsv I4 and an anode I5. The cathode II' is connected internally of the .tube to the beam-forming plates.

-Externally, the cathode I I is connected through an Vadjustable resistance I6 and the complete resistance portion of a potentiometer I1 to the negative terminal'of a source of directr current,

tive so that, with an increase in the current such as a battery I8. TheY negative terminal of the battery is also connected to ground, as shown. The anode I5 of the tube isr connected through an inductance I9, which forms the primary winding of an iron-core transformer 20, and

an adjustable resistance 2| to the positive terminal of the battery I8.

The control grid I2 of the tube is connected through an inductance 22 forming a secondary winding ofthe transformer, to an intermediate tap on the resistance element of the potentiometer I'I. Theescreen grid I3 of the tube is y connected through a xed resistance 23 andthe adjustable resistance 2l to the positive terminal of the battery I8.

The output circuit for the current wave gen- The screen grid I3 of the tube IllA may be con- 4.

nected to a terminal 30. The junction point of the iixed and adjustable resistances 23 and 2 I' respectively, may be coupled by means of a blocking condenser 3| to a terminal 32 which is connected to ground. There may be applied to terminals v3i) and4 32 synchronizing pulses for the purpose of correlating the operation of the oscillator with the signals applied to the control element of the cath- Vode ray tube.

Where it is desired to utilize the high voltage appearing periodically at the anode I5 of the tube I 0, there is provided arectier tube 33 having its anode connected to the anode I5 of the tube I 0 and its cathode connected to an auxiliary winding 34 on the transformer 20 which is utilized for heating purposes. The cathode of the rectiier tube is connected to a positive direct current output terminal 35. The negative direct current output terminal 36 is connected to ground and is Vcoupled toterminal 35 bya iilter condenser 31.

Considering now the operation of the apparatus illustrated in Fig. 1, reference will be made to certain observable characteristics of the oscillator before considering a suggested theory4 of operation which will be oiered subsequently. Accordingly,

the voltages which are known to exist at certain times in the various circuits associated with the f elements of the beam-power tube will be referred to Such yoltagesare illustrated by thecurves of Fig. 2.

' The connection of the circuit of the control grid I2 to the resistance element of the potentiometer I 1,-vv introduces into this circuit a negative bias potential produced by the ow of cathode current Ithrough the resistance. However, the poling of Vthe transformerwindings I9 and 22 is regenerathroug'h the'primary Winding I9, a positive potential derived from the secondary winding 22 is also introduced into the control grid circuit. During periods of current increase in the primary windingthe positive potential is of suiiicient magnitude topredominate over the negative potential and to thereby render the control grid sufficiently positive to reduce the impedance of the tube I0 to a relatively low value. 'During periods of current decrease vinthe primary Winding a negative po'- tential, derived from the secondary winding 22, is introduced into the control grid circuit which, in itself, is sufiicent rtoincrease the impedance of the tube I U 'to infinity. There is also provided a positive biasfor the screen grid I3 which is of a predetermined minimum magnitude depending upon the values of the iixed resistance 23, the adjustable resistance 2| and the voltage of the battery I8.

A cycle of operation will be assumed to start with the closing of the cathode-to-anode path within the vtube I'Il. Current starts to flow in the series .circuit comprising the battery I8, the adjustable resistance 2l, the transformer primary lWinding I 9', the space current path of the tube IIJ, the adjustable resistance I6 and the resistance element of the potentiometerV Il.

Theimpedance ofv the anode-to-cathode path within the tube constitutes the major part of the resistance portion of thecircuit. .Consequently the impedance of the variable resistance I6 and th'e potentiometer I'I may be neglected for the present purpose. By reason Yof the inclusion of the inductiveprimary Winding I9 in this circuit, the current increase with respect to time is gradual. During the time that the current is increasing in this'circuit, the potential of the Vcathode I I of the beam power tube I0 is becoming more positive, as indicated by the curve 38 of Fig. 2. At the same time, the potential'applied to the screen grid I3 of thel tube is becoming increasingly positive, as indicated by the curve 39. Concurrently Ywith these voltage changes, Athe voltage of the-anode I5 of the tube remains at a substantially constant negativevalue, as indicated by the curve 40. Also the potential applied `tothe control grid I2 similarly remains at a substantiallyponstant value which is positive, vas indicated by the curve 4I. These conditions exist Vfor a period of time which, it has been found, is'determined primarily by the ratio of the inductanceexternal of the tube I Il to the internal resistanceV of the tube included in the series anode-to-cathode circuit of the tube. If no synchronizing signals are applied to the terminals 30 and 32 and the oscillator is permitted to function under the sole influence of the self- `excitation provided, the current increase between the cathodeandanode of the tube I0 suddenly VstopsV when Va critical inter-electrode potential relation is reached and a sharp decrease, in this currentv ensues. complete interruption of the current iiow is eiected in a much shorter time 5, than yingpri-or art devices; such asthe Farnsworth oscillator. K

At thispoint the lanode voltagerises momentarily to a 'rsharpposit'ive pe'a'k indicated I-b'y the curve '42. The amplitude of this peak is conside erably in `excess ofthe voltage of thel battery Hl; Also, at thistnne, the "potential-ofthe fc'oritrol grid I2 lis momentarily 'reduced to Sa lhigh negative value which is in excess Vof the negative biasing effected Aby the 'self-'biasing yresistance element of the Ypotentiometerv II, ThisA momen-v tary negative potential is'represented:bythe-'curve 43. Coincidentally 'with the Vappearance of these potential peaks, the positive potential of the screen grid I3 vrises sharply to-a value'whi'chis substantially equal to that of 'the battery I8; This potential change is indicated by the curve fbi. Also, the' potential of the cathode II` is suddenly reduced to zero, las indic'atedby the curve 65. The potentials represented by the'curves 42, 43', 134' and 45 kexist only for theshort period 'of time that the cathode-toeanode current is interrupted. The potentials ofthe tube elements then revert `to their initial polarities land values, resultingin the reclosing ofthe'cathode-to-anode 'path within the tube 'I0 and the repetitionl of'the described cycle.

The output circuit connected to terminals 2d and Z5'is'd'erivedby connectionsmade respectively to thecontrol grid I2 and to theslider 26` of the potentiometer I1. -Consei'iu'ently, 'the' potential appearing at the 'terminals 24 and 25 varies in accordance with the variation of thev control grid'potential' with respect toth'e potential of the 'cathode'. From the curves 'of Fig. 2, it 'is seen that, during thernajor portion ofthe cycle, the

control grid potential has a substantially uniform value Whilethe cai-,bodeA potentialhasan increas- 'ingvalue It is readily seen, therefore, that the potential of the output circuit has a complex YWave form which is substantially a saw-tooth form as indicated by the 'curve '46. The current flowing through the circuit connected to terminals 24 and 25, therefore, has a Wave form'suitable for the creation of an electromagnetic 'iield 'by the deection coils 2 which has a saw-'tooth form. For Athe purpose of absorbing any exponential component which may appear in thegen'- erated current wave, there 'is provided a series network of vthe ihductahcefa and theY IeSlS'tIlC g 29 connected in shunt with the deflection' coils 27.

'The frequency of' the current Wave produced by the oscillatorembodying thel present invention, is determined primarily by the ratio of the external induotance represented by the primary Winding I9` of the transformer 20, to the internal .resistance of l.the tube I0. 4These frequency-determining yfacilities are substantially different from the facilities provided for a similar purpose inthe oscillator disclosed in the Farnsworth patent referred to. In the .Farnsworth osci1lator, the frequency control` is elected by adjusting lthe value ofthe grid-leak resistance connected from the control grid to ground. The corresponding element in thepresent oscillator is the right-hand portion I'I of the resistance Velement of the potentiometer II. In the oscillator, in accordance with the present invention, variation in the frequency of the generated current wave may be effected by varying either the 'inductance of the winding Igor the 'resistance of 'the'tube I0. Itis most conveniently eifected by varying the value 'of the adjustable resistance' I6 vwhich thereby they internal resistance or the tube is changed,

6 thereby altering" the mauctaesr-resstane tio-of the-'cathode-"to-anode series circuit. vIt has been found that the `actual 4impedance vof the primary andsecond'ar'y transformer windings I9 andZI respectively, arenot'at allcritical for the successful oper-'ation of the oscillator- The adjustment of the variable resistance 2l e'iects a control of the amplitude of the high peaks-of anode voltages produced by the opere ation fofthe present oscillator, and also controls the speed 'of the generated current Wave. The latter control determines the time required for the generated current Ywave to change from its maximum to its minimum value'. |Ilhe adjustable resistance-2l also controls the susceptibility of the oscillator Ato synchronizing pulses. It has been found that for every design of an -oscillator of `this type there are certain optimum values of impedance -and positive potential connected 1go-the screen grid I3'.

If synchronizing potential pulses of negative polarity and predetermined magnitude lare applied' -to terminals VSEII' and 3'2 ata slightly higher frequency than the free loscillation frequency of the current Wave generator, the 'cathode-toanode vcurrent interruptions are induced thereby slightly xbefore the occurrence-of thedescribed self-induced interruptions. Thus, one cycle is ended and anew one startedin synchronism with the synchronizing pulses;

The apparatus connected in `the mannerv described arrd-illustrated in Fig. 1, has been found to give satisfactory resul-ts for the purpose described when using -circuit elements and con stants in accordance With the following table: Tube lOl-Type SALGG! Variable resistance .i6-100. ohms; .2 watts Potentiometer resi-stance 17460 ohms; 2 Watts Battery 18-300-400 Volts PrimaryY winding -19--660 .mill'ihenries; 700 turns Secondary winding 22-10 mi1lihenries;. 85 turns Fixed resistance23'-5000 ohms; 1'0 Watts Variablelresistance2156000 ohms; 10 watts Deecting coils27ll2.l5 rnillihenries Inductance 28-3.5 millihenries Resistance 29--1000 ohms; `l0 watts Itis believed ithata yfullerappreciation of the marked distinction` of the-oscillator embodying the present invention over prior art oscillators maybe derived lfrom a consideration of the fol-4 lowing suggested theory' of operation. It seems evident from a study of 'ithe curves of Fig. 2, that Ithe interruption of the cathode current, once it is started, is :accelerated at such a high rate that the current cut-off is relatively absolute. The acceleration is apparently caused by the'negative impulsive 'potential of the control grid I2, as vindicated by the peak 43. This potential is developed by the regenerative coupling of the vtransformer windings I9 and 22 in` response to the slight `lessening of the rate of -increase of the cathode current. Up to a certain point, this 'rate of increase i's constant. As the cathode current starts to increase, it isseen 'from the curve 39 that the potential of the screen grid I3 is at its lowest value. This is probably due to the 'de'ection of a large number'of electrons toward the screen grid at this time. As'the-cathode current increases, the potential-'ofthe cathode also increases, as evidenced by the curve 38. potentials of the beam-forming electrodes I4 also increase similarly since they are vconnected "internally of *thel tubev to 'the cathode II. It appears likely'th'atas the Jpotentials vof the beam- The forming electrodes increase, the number of' electrons which are deiiected toward'the screen grid decreases at the same rate until the poten-tial of the screen grid reaches a value at which a part of the electron beam Vstrikes the beamforming electrodes. This action vinitiates interruption of the cathode current whichthen, because of the regenerative action of the device, completely ceases substantially instantaneously.

Control of the deflection amplitude of the electron beam under the influence of the deecting coils 21 may be effected in a number of ways. In Fig. 3 there is provided in series with the deecting coils an adjustable inductance device 48 by means of which a variation in the deflection amplitude may be secured.

In Fig. 4 the deflecting coils 21 are shunted by a series network similar to that shown in Fig. l. In this case, however, the reactive element is an adjustable inductance device 49 and the nonreactive element is an adjustable resistance 5D. A variation of the value of the adjustable inductance 49 effects the desired change in the deflection amplitude. However, since any change in the value of this element alters the effectiveness of the shunting circuit as a means for refining the wave form of the deflection currents, an adjustment of the resistance 55 is necessary to maintain the wave form correcting effectiveness of the circuit at an optimum value.

In Fig. 5 the arrangement of the circuit elements comprising the oscillator is, with the exception of certain refinements which will be described presently, substantially identical w-ith the arrangement of Fig. 1. For the purpose of eifecting still another control of the deflection amplitude, there is provided in the connection between the anode of the tube i and the anode of the rectifier tube 33 an adjustable resistance l. By means of this device, the magnitude of zthe direct current appearing at the terminals 35 :and 35 may be varied.

In the case where this .direct currentis used as the source of potential for the second anode of a cathode ray tube, variations in the value of the direct current changes the stiiness of the electron beam in the cathode ray tube. In consequence of such a change a corresponding variaticn in the magnitude of the defiection of the beam is effected.

Fig. 5 also discloses facilities for changing the nominal frequency of the current wave generated by an oscillator of this type without changing the amplitude of the current. Such an arrangement provides a convenient device for adapting a television receiver for use in receiving sign-als transmitted according to a plurality of different standards.

rIhe frequency of the generated current wave produced by an oscillator in `accordance with the instant invention is determined by the ratio of the deflection current constant when a frequency change is effected by the means described, it is necessary to effect a compensatory change in the transformer ratio. Such a change is effected by the facilities herein provided by decreasing the number of turns on the secondary winding Whenever the current through the primary winding is decreased as a result of an increase in the resistance of a primary circuit. A compensation of this character is necessary for the additional reason that the different reactance of the deflecting coils 21 at the new frequency is reflected in the anode circuit ofx the tube I0. The reflection, of course, is by reason of the transformer coupling between the anode and grid circuits, the latter of which is connected to the deflecting coils.

There is shown in this figure an additional relatively low fixed resistance 52 connected in the external cathode-to-anode circuit. The terminals of this resistance are connected to a switch 53. The secondary winding 54 of the transformer 20 is provided with an intermediate tap 55 which is connected, together with the terminal 56, to another switch 51. The switches 53 and 51 may be ganged in the manner shown for simultaneous operation.

With the switches 53 and 51 in the `positions shown, the resistance 52 is short-circuited and the entire secondary winding 54 is connected in the control grid circuit. The oscillator functions to generate a current wave of a frequency determined by the ratio of the inductance of the primary winding I9 to the resistance of the anode-to-cathode circuit of `the tu'be I0. When it is desired to change the frequency of the genof the external anode inductance to the internal anode-to-cathode resistance of the beam power tube. As previously described, the most convenient means for changing this ratio is by a variation of the grid bias effected by the adjustment of one of the external Vresistance elements. Obviously, such a change `will alter the magnitude of the current flowing in the circuit. This current traverses the primary winding I9 of the transformer 2U. The value of the deflection current is a function of the product of the current iiowing in the primary transformer winding l5 and the ratio of the primary winding to the secondary winding. Therefore, in View of this relation, if it is desired to maintain the value erated current Wave by a predetermined amount, the switches 53 and 51 are moved to their left hand positions. VThe short circuit is removed from the resistance 52 and the number of turns on the secondary winding 54, which are included between the intermediate tap 55 and the terminal 56, are disconnected from the control grid circuit. As a result of the removal of the short circuit from resistance 52 there is a decrease in the current flowing through the primary winding I9. Coincidentally, however, the ratio of primary-to-secondary turns on the transformer 20 is increased in an amount sufficient to compensate for the decrease in the primary current and for the changed reactance of the deflecting coils 21. By properly choosing the value of the resistance 52 and the number of secondary turns which are switched into and out of operation, it is obvious that the value of the deflection current can be maintained substantially constant. It will also be obvious that the oscillator may be arranged to operate at several predetermined frequencies without substantially changing the value of the deection current by providing additional resistances similar to resistance 52 and additional secondary taps similar to the intermediate tap 55, vtogether with yadditional switch contacts connected to the added facilities, in a manner similar to that shown.

In Fig. 6 there is shown an alternative means for producing a current wave of the desired form without the use of a shunting network around the deflecting coils as illustrated in Figs. 1, 4 and .5. It is well known that such shunting networks function by absorbing the semi-exponential component of the generated current device functioning in this manner absorbs power which, in most cases, may be vused more advantageously for deflection pur '9` poses. VIn the arrangement of lig. 6` such. a shuntinginetworki 'is notv required.. The transformer 2!) is provided, in vadditionto the usual secondaryA windingl` 58,- with' yaii-..a;uxilia ry Vwinding 59. In series with; the Vauxiliary Winding is. a condenser 60 and; the.A network so formed is connected t'othe terminalsof-a resistance lewhich is inserted between the -secondary winding58 and the'controlgrid l-2aof thebeam powertube l0. vSuch an -arrangementprovides 1an eiective compensation'for the non-linearityA of the tube characteristic and, hence, tendsr to` linearize the generated current wave.

The use. of an cscillatorinaccordance withl the present invention provides several advantages overY the useof any prior art deviceof. this type. 'I-'l-ie chief advantage is in obtaining a current wave suitablefor deection purposes which is of considerablyY greater magnitude than it has beenpossible to obtainheretofore. Another advantage isthat thegformof. the generated current wave is, inherently more linear than heretofore obtainable. Another, advantage isthe increased' speed, of the current, Wavev resulting in a faster return time;

While there has been described what is at present considered the preferred embodiment of the invention, it will be obviousto-those` skilled inthe art that various. changesand modifications may b e made. therein without departing from the invention, and it is, therefore, aimed in the appended claims to: cover all. suchA changes andmodifications as fall within the true spirit and scope of the invention.

What I- claimris: Y

1. lAn oscillatorY for -generating a saw-tooth Wave comprising,4 anl electronic vdevice having input and output circuits and internal: resistance, -an external: circuit coupled to said outputcircuit including an inductance, andany external circuit coupled tosaidl input, circuit including a second inductance regeneratively. coupled to said irst inductance, said electronic'device being at tube of the beam.- power type wherebyy the frequency of the generated Wave is determined by the ratio of said youtput circuit` inductance tosaid internal resistance, and avariable extemalresistanceconnected in common. to said input and output circuits Yto vary said internal resistancewhereby to changeY the frequency of the generated Wave.

2. An oscillator for generating a- -sa-W-tooth wave comprising; an electronic device yadapted to form a concentrated electron beam and having a cathode, an anodeiandltwo,grid'lelectrodes, means for maintaining one of said grid electrodes at a predetermined positive potential, an input` circuit for said device including the kother of said grid electrodes and a variable resistance connected to said cathode, an output circuit for said device including said anode,.said cathode and-the series-Connection of an inductance andaidfVari- -able resistance, and means. including said; inductance. toregeneratively couple-said input and output. circuits, said resistance -servingA to `ccntr-ol the internal resistance o-said electronicfde- -vice and thereby the frequencyI ofsaid generated Wave. v '3; An oscillator for generating-a-.saW-tooth current Wave comprising, a, beam power tube having a cathode, an anode, two grid electrodes and internal resistance, a first external circuit connecting, said cathode .andfsaidz anode: including. an inductance and a resistance, the ratio of said inductance to said internal resistance being the frequency-determining factor of said generated wave a second external circuitvconnecting said cathodewith one of said grid. electrodes including the; resistance ofsaid'iirst external circuit and an inductance'regeneratively coupled to the inductance of saidyfirstcircuit, and means to maintain the other.l of'gsaid grid electrodes ata positive potential with respect to said cathode for determining the amplitude of said generated wave.

4. oscillator for generating a currentv wave of L complex form suitable for-creating a magnetic eld. having; -asaw-tooth formA comprising, al beam power tube having"a--cathode-, an: anode, a' control grid, a` screengrid and acontrollable internal resistance, anV external resistance connected at one end' to said cathode,y an anode inductance con'- nect'edrbetween` said anode and theV other end of said external resist-ancethe ratio of said inductance to saidV internal resistance being the principal factor in determiningt-he frequency of said current wave, a control grid inductance connected'. between said; control gridV and lsaidot-her lendof said'external'fres-istance and regeneratively coupled*` toV said;` anode inductance,v said external resistance providing .ai control" of saidinternal resistance, ank output circuit for said current wave derived from said'. control grid-inductance, and a sourceof direct current potential connected between mid. screen grid and said-cathode fordetermining the amplituder of. said Vcurrent wave.

5. An, oscillator for generating a sawftooth wave comprising, a: beam fpower tube having a cathode, an. anode-,a;control grid, a screen `grid and? internal',resist-ance, an external resistance connected to saidY cathode, a transformer having primary andi secondaryV windings, a source of direct current energy,v a. frequencyedetermining circuit` connecting Vsaidv cathode and said anode and. including a series'. arrangement of said internal resistancersaidisourcel of energy and'said-primaryl transformerwinding, aregenerativev circuit connecting said cathode andsaid control :grid and includingra series arrangement of said external resistance andA saidl secondary transformer winding', an output circuit for said saw-tooth wave derived from said'. secondaryy transformer winding; and a circutfor' determinin-gthe amplitude cf. said. saw-tooth wave including. a positive potential connected tosaid1screen grid.

16. oscillatorf'cr generating a saw-tooth wave comprising; an electronic' device having; input andV output circuits. and internal resistance, arr externalcircuit coupled'to saidoutput circuit including` an inductance and: a resistance, anexternal'l circuit coupledzto said input circuit including a second inductance. regeneratively coupled to*v said firstinductance,l the frequency ofthe generated wave being determinedby-the ratio of said output circuit inductance to saidv internal resistance, said externalfresistance-*being variable to change said internal' resistance and, thereby, the frequency of' the'v generated wave', and means for 'concurrently varyingv said input circuit inductance to maintain` a constant amplitude of the generated wave irrespective of. thefrequency 'thereof'.

7; `In a circuit including an inductanceY anda resistance, the combination for controlling the rates of"increaseandi decrease of current inpsaid circuit' including, an. electronicA device having: a cathode, an anode' and' a control grid, th'ezcathode-toanode internal Acircuit constituting said resistance', the cathode-to-anode external circuit including "sa-id inductance and a scifi-biasingV im'- pedance device connected to said cathode, said .cathode being biased by said impedance device in accordance with the vmagnitude of said current and the gridV serving to contr-ol said resistance, and means for regeneratively lcoupling said grid to said external circuitwhereby the rates of current increase and decrease cause abrupt changes of said resistance and whereby said resistance changes in turn eiect changes in said rates of current increase and decrease.

8. An oscillator for generating a saw-tooth wave comprising, an `electronic device having input and output circuits and internal resistance, a rst inductance element coupled'to said input circuit, and impedance device conductively coupled in common to said input and output circuits, and a frequency-determining circuit including the internal resistance of vsaid electronic device and a second inductance element coupled to said output circuit and regeneratively coupled to said rst inductance element.

9. An oscillator for generating a saw-tooth current wave comprising, a beam power tube having a cathode, an anodeand a grid by which to control the internal resistance of said tube, an anode inductance device and a resistor connected in series between s aid anode and said cathode, the ratio of said anode inductance to said internal resistance being the principal factor in determining the frequency of said current wave, and a grid inductance device connected between said control grid and said resistor and regeneratively coupled to said anode inductance device.

10. An oscillator'for generating a saw-tooth current wave comprising, a beam power tube having a cathode, an anode and a grid by which to control the internal resistance of said tube, an anode inductance device and a resistor connected in series between said anode and said cathode, the ratio of said anode inductance to said internal resistance being the principal factor in determining the frequency of said current wave, a grid inductance device connected between said control grid and said resistor and regeneratively cou-` pled to said anode inductance device, and an output circuit for said current wave derived from said grid inductance device.

11. An oscillator for generating a saw-tooth current wave comprising, a beam power tube having a cathode, an anode, a screen grid and a control grid by which to vary the internal resistance of said tube, a series external anode-to-cathode circuit including an anode inductance device connected to said'anode and a resistor connected to said cathode, the ratio of said anode inductance to said internal resistance being the principal factor in determining the frequency of said current wave, a control grid inductance device connected between said control grid and said resistor and regeneratively coupled to said anode inductance device, and a source of synchronizing signals coupled in negative polarity to said screen grid.

12. An oscillator for generating a saw-tooth wave comprising an electron discharge' device having an anode, a cathode, a control grid, a screen grid and an electrod-e connected to said cathode for suppressing the flow of secondary electron current from said anode to said screen grid, an anode inductance device and an impedance device connected in series between said anode and said cathode, the ratio of said anode inductance device to the internal resistance of said electron discharge device being the principal factor in determining the frequency of said sawtoothwava a grid inductance device connected between Asaid control grid and said impedance device and regeneratively coupled to said anode inductance device, means including a resistor for impressing upon said screen grid a positive voltage with respect to said cathode, and means for impressing synchronizing signals of negative polarity upon said screen grid.

13. An oscillator for generating a saw-tooth wave comprising, an electron discharge device having an anode, acathode, a control electrode to vary the internal resistance of said device between said anode and said cathode, a screening electrode to minimize the interelectrode capacity between said anode and said control electrode and a suppressor electrode connected to said cathode for minimizing the W of secondary electron current from said anodeto said screening electrode, a rst inductance device coupled to said anode and an impedance device connected in series therewith and coupled to said cathode, the ratio of said iirst inductance device to the internal resistance of said electron discharge device being the principal factor in determining the frequency of said saw-tooth wave, and a second inductance device coupled between said control electrode and said impedance device and regeneratively coupled to said rst inductance device.

14. An oscillator adapted to drive a substantially saw-tooth current wave through an electromagnetic ray deflecting coil of a cathode ray tube comprising, an electron discharge device having an anode, a cathode, a control electrode to vary the internal resistance of said device between said anode and said cathode, a screening electrode to minimize the interelectrode capacity between said anode and said control electrode and a suppressor electrode connected to said cathode for minimizing'the ow of secondary electron current from said anode to said screening electrode, a rst inductance device coupled to said anode and an impedance device connected in series therewith and coupled to said cathode, the ratio of said ilrst inductance device to the internal resistance of said electron discharge device being the principal factor in determining the frequency of said saw-tooth Wave, a second inductance device coupled between said control electrode and said impedance device and regeneratively coupled to said ilrst inductance device, and an output ycircuit conductively coupled to said second inductance device.

' MADISON CAWEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED 'STATES PATENTS 

